Differences between POP3 and SMTP E-mail

SMTP is a long established Internet protocol that is used for the delivery and receipt of e-mail. POP3 is also an Internet protocol but is used only to collect e-mail.

When configuring your e-mail software (e.g. Outlook or Outlook Express) you always need to specify the name or IP address of the SMTP server for outgoing e-mail. This name or address is normally provided by your Internet Service Provider (ISP).

Note, that it is perfectly possible to have one ISP just for Internet access and another service provider to host your e-mail. However, many ISPs include e-mail as part of their Internet access package.

To collect e-mail you have a choice of POP3 or SMTP. However, you can only use SMTP with software that is SMTP aware such as Microsoft Exchange. Outlook and Outlook Express cannot on their own receive e-mail using SMTP.

With SMTP you need to have a static IP address on the computer that is running your e-mail software. Whoever is hosting your e-mail domain name will attempt to deliver e-mail to your e-mail server as and when e-mail arrives and regardless of who the e-mail is addressed to. Your e-mail software is responsible for organising which e-mails go into which inboxes. If your e-mail server is off then your e-mail service provider will store the e-mail for you until your e-mail server can be contacted again.

The main advantages of using SMTP to receive e-mail are that e-mails arrive more or less immediately at your server and that you do not have to set up individual mailboxes with your e-mail server provider.

With POP3 you need to set up an account, with your e-mail service provider, for each e-mail address that you wish to use called a mailbox. When e-mail is sent to your domain the e-mail will be stored in the appropriate POP3 mailbox until you collect it. Your e-mail software has to actively connect to the your e-mail service provider's server to check if there is any e-mail and then download it. This must be done separately for each mailbox. Most e-mail clients can be configured to automatically check for new e-mail every few minutes.

E-mail service providers use a variety of charging schemes for SMTP and POP3 Mail. Some charge to provide SMTP mail, others charge for each POP3 mailbox. Some ISPs include a specific number of POP3 mailboxes for free as part of a package.

In general, businesses that use an e-mail server such as Exchange should use SMTP for incoming e-mail.